Medical treatments involving ablation of the endometrium of the uterus are well known in the prior art. The endometrium is the portion of the uterine lining to which an embryo normally attaches and is responsible for the menstrual cycles. Such ablation treatments typically involve either the direct or indirect application of heat or cold to the endometrial tissue. Commonly, ablation devices and techniques have been used to treat menorrhagia (a condition of excessive menstrual bleeding) by cauterizing, or inducing necrosis of the endometrial lining. This cauterization prevents further proliferation of the endometrium and may result in permanent relief of menorrhagia symptoms.
Apparatuses for thermal balloon ablation are well known in the prior art. For applications to treat the endometrium of the uterus, thermal balloon ablation apparatuses typically comprise a distensible balloon which is inserted into the uterus through the external opening of the cervix. The balloon is then inflated with a liquid to expand the balloon such that it is in contact with substantially all of the uterine cavity. This liquid is then heated to a controlled temperature by a heating element within the balloon and the liquid is maintained at this temperature for a predetermined period of time. After this period of time has elapsed, the liquid is withdrawn and the balloon removed from the uterus. The heat energy which is transferred from the liquid filled balloon to the surrounding tissues of the uterus causes the desired cauterization of the endometrium. There are many examples of such devices in the prior art, for example those disclosed by Stevens et al—U.S. Pat. No. 5,800,493, and Wallsten et al—U.S. Pat. No. 5,693,080 & U.S. Pat. No. 5,571,153.
Typically the volume of liquid required to inflate the balloon ranges between 5 ml and 30 ml and is dependent on the natural volume of the uterine cavity and the liquid pressure. According to studies published in the medical literature, the liquid pressure should not exceed 180 mmHg applied to the uterine cavity walls above which there is risk of mechanical damage to the deeper tissue of the uterus.
Variations on thermal balloon apparatuses and methodologies include cryogenic apparatuses which use cooled liquid rather than heated liquid to achieve necrosis of the tissue (such as that disclosed by Lafontaine et al—U.S. Pat. No. 5,868,735) and apparatuses in which heated liquid is circulated through the uterus without the benefit of a flexible balloon to contain the liquid (such as that disclosed by Goldrath—U.S. Pat. No. 5,437,629).
A variety of alternatives to thermal balloon ablation are known for cauterization of endometrial tissue. These includes the use of microwave, RF, laser, electrical current or similar energy sources to heat a surgical probe inserted through the cervix and which is manipulated by means of direct hysteroscopic visualization. These devices typically require a highly skilled operator and produce treatment results which are more variable than those which can be achieved through thermal balloon ablation techniques. Such alternative ablation techniques also pose higher risk of perforating the uterus, normally require use of general anesthesia, and have a higher incidence of post-operative complications than thermal balloon ablation techniques.
In spite of the potential advantages of thermal balloon ablation techniques over alternative treatment methodologies, problems with the thermal balloon ablation apparatuses in the prior art have prevented such devices from being adopted widely for use in the treatment of menorrhagia.
Thermal balloon ablation systems in the prior art typically rely on heating elements located within the balloon. During heating, these devices often develop temperature gradients in the liquid which can result in uneven treatment of the endometrial surface. Typically the observed effect is to over-treat the area of the endometrium directly above the heating element and under-treat the area of the endometrium located directly below. This effect is magnified if the heating element within the balloon is inserted at an angle relative to the anterior/posterior plane of the uterus such that after inflation the heating element is located closer to the anterior wall of the balloon. Placement of the heating element relative to the balloon walls is difficult to control in practice. To reduce this problem, some inventions in the prior art include provision of an impeller, reciprocating piston or similar mechanical means to stir the liquid during heating (such as those disclosed by Neuwirth et al—U.S. Pat. No. 5,460,628 and Saadat et al U.S. Pat. No. 5,827,269) or utilize balloons which allow injection and re-circulation of heated liquid via multiple lumens, typically an “intake” lumen and an “exhaust” lumen (such as that disclosed by Lafontaine et al—U.S. Pat. No. 5,868,735). Furthermore, pulsing the liquid pressure is an alternative means to achieve more uniform mixing of the liquid (as described by Wallsten et al U.S. Pat. No. 5,957,962). However, such circulating methodologies add cost and complexity to the apparatus and the ability to achieve desired temperature uniformity depends among other factors on the volume of liquid within the balloon.
Thermal balloon ablation devices in the prior art such as that disclosed by Stevens et al—U.S. Pat. No. 5,800,493 have also relied on the operator to provide the liquid for inflation of the balloon and heating. This has limited the variety of liquids to those typically found in a clinical environment (e.g. D5% W or saline). Such liquids are generally water based and therefore cannot be heated above approximately 100C, at which temperature these solutions begin to boil at sea level. Heating liquid to the boiling point can result in a dangerous increase in balloon volume due to expansion of gas and in uneven treatment since the presence of this gas pockets in the balloon act to thermally insulate the adjacent tissue. The maximum temperature limitation of these liquids has resulted in relatively long treatment times; it is well established in the research and in clinical practice that it requires in approximately 8 minutes to cauterize the endometrium by thermal balloon ablation using liquid temperatures of 85 C. Furthermore, the use of liquid temperatures in the range of 70-90 C makes the use of liquid heating means external to the uterus or balloon ineffective since in this temperature range there is insufficient heat energy contained within the volume of liquid within the uterus to adequately cauterize the endometrium. In devices that employ heating means external to the balloon in the uterus and which use liquid temperatures below 100 C (such as that disclosed by Chin U.S. Pat. No. 5,449,380) it is generally necessary to continuously circulate the liquid between the balloon and the external heating means in order to maintain an elevated liquid temperature within the uterus and to achieve the desired treatment. In addition, devices with heating elements located in the balloon within the uterus prohibit the use high viscosity liquids (such as 100% Glycerin) which resist flow at ambient temperatures but once heated become less viscous and can readily flow through a catheter to inflate a balloon placed in the uterus.
Systems which require the operator to supply the inflation liquid are also complicated for the operator to use. It is necessary for the operator to obtain a source of sterile liquid, inject the liquid into the system, check for leaks, purge gas or excess liquid from the system, and then dispose of the heated liquid after treatment. This process also compromises the sterility of the system since there is potential for non-sterile or contaminated liquid to circulate within the balloon. In the event of a balloon leak or rupture, this non-sterile liquid is released into the uterine cavity and could result in infection.
Devices in the prior art typically rely on mechanical actuators, syringes, or liquid pumps which come into contact with the treatment liquid in order to control inflation and pressurization of the balloon, these can be expensive, unreliable, and subject to contamination. Often these systems require the operator to manually inject liquid to fill the balloon. Furthermore such systems (such as that disclosed by Stevens et a—U.S. Pat. No. 5,800,493) typically have expensive disposable components as these components often include hoses, valves, connectors, electrical wiring, syringes, and heating elements which must be disposed of after each use. Wallsten et al have attempted to address this problem in the invention disclosed in U.S. Pat. No. 5,957,962 in order to provide an inexpensive disposable component however the described system still requires the addition of liquid from an external source, purging of gas from the system and relies on a mechanical apparatus and actuators to inject and remove liquid from the treatment balloon.
Often it is difficult for the operator to control inflation pressure and there is not adequate means to control this pressure in response to changes in uterine volume during treatment (typically the uterus relaxes and expands as treatment progresses and therefore it is desirable to increase the volume of liquid in the balloon to maintain a constant inflation pressure). Wallsten et al U.S. Pat. No. 5,693,080 discloses apparatus intended to allow automated control of inflation pressure through mechanical actuation of syringes or similar means however this is costly and does not allow fine control of pressures. Wallsten et al further disclose a means for providing overpressure relief in the event of a increase in balloon pressure such as that which might be caused by a sudden contraction of the uterus during treatment however this does not provide a practical or inexpensive means for automated control of balloon inflation, deflation, and liquid pressure.
Prior art devices also rely on the operator to sound the depth of the uterus then insert a catheter or treatment element to a depth of no greater than the previously sounded depth. This requires effort on the part of the user to measure depth and observe insertion depth as marked on the treatment device. There is a danger of perforating the uterus by over-inserting the catheter if the clinician does not perform this operation properly.
In providing thermal balloon ablation treatment, it is desirous to: provide uniform cauterization of the endometrial tissue; ensure that any material which can potentially come into contact with the patient is sterile; provide the treatment in as short a period of time as possible; deliver the treatment in a manner which does not depend on the skill level of the operating clinician; and minimize the cost of any disposable components associated with the treatment apparatus. It is further desirable to avoid cauterization of the cervical canal during treatment, and to minimize the risk of perforation of the uterus when the balloon is inserted through the cervical opening or during the treatment period.
Ideally the device should be simple for the operator to use and should require minimal preparation for use by the operating clinician.
Accordingly, the present invention provides an apparatus for causing necrosis of a body cavity or duct, specifically the uterus, said apparatus comprising:
a disposable portion of the apparatus comprising a sealed system consisting of a liquid within said sealed system, an elongated distal section with a flexible balloon (or bladder) attached to it, a proximal flexible balloon (or bladder), and a means for connection to a permanent non-disposable apparatus;
a means for heating said liquid; and
a permanent non-disposable apparatus comprising, a pneumatic pressurizing means for initiating flow of the liquid within said sealed system of the disposable portion of the apparatus, connection means for said disposable portion to permanent portion, and a controlling means for heating, pneumatic pressure, and time.
An object of the invention is to provide an apparatus which furnishes a means for shortened treatment time by incorporating a sealed disposable component containing a volume of liquid provided by the manufacturer. A liquid filled and sealed disposable apparatus provides one advantage as it allows the use of liquids which are not typically encountered in a clinical environment and which can be heated to temperatures in excess of 100 C without boiling (for example 100% Glycerin). This allows improved cauterization of the endometrial lining of the uterus and shortens treatment times from 8 minutes at 85 C to approximately 1.5 minutes at 165 C. Furthermore, by pre-heating the liquid external to the patient, high viscosity liquids (such as 100% Glycerin) can be used which flow readily at higher treatment temperatures. Because of the high viscosity at ambient temperatures, such liquids could not be readily utilized in apparatus where the heating means is located inside the balloon which is inserted into the uterus.
Another object of the invention is to provide a means of ensuring uniform treatment of the uterine cavity. The apparatus achieves the objective by injecting a pre-heated, isothermal volume of liquid into the distal flexible bladder within uterine cavity. Therefore at the time of injection into the uterus, all areas of the uterus are contacted with a uniform high temperature (approximately 165 degrees Celsius) liquid.
Another objective of the apparatus is to provide a low cost, easy to use system, that is safe and effective. The described apparatus provides for improved ease of use and reduced costs by using a disposable component comprising primarily: two flexible enclosures joined by a liquid path and containing a liquid; and a fitting which permits the proximal flexible enclosure to be sealed inside the re-usable pneumatic chamber. By using a sealed system containing a bolus of liquid, the operator simply installs the disposable cartridge and initiates heating. There is no need to source liquid, fill the system, or purge gas from the system. This makes the apparatus much easier to use and improves patient safety by ensuring sterility of the system. Since the liquid is contained in a sealed system and is driven by pneumatic means, in the event of a balloon rupture only sterile liquid can be released into the uterus. The disposable component does not include valves or fluid pumping means and can therefore be manufactured for minimal cost.
A further object of the invention is to automate balloon inflation and control of balloon inflation pressure. The described apparatus provides improved control of balloon inflation pressure by modulating pneumatic pressure within a chamber external to the patient. This pressure can be readily monitored and automatically controlled with a high degree of accuracy to achieve the desired inflation pressure of the distal balloon during the treatment period, adapting quickly to changes in uterine volume due to relaxation or contraction of the associated musculature. By using pneumatic pressure to transfer liquid from the proximal flexible balloon into the distal flexible balloon and withdraw liquid from the distal flexible balloon, the system achieves a high degree of control and reduces user errors.
Yet another object of the invention is to provide a physical means to indicate when the proper depth of insertion of the balloon is achieved. The described apparatus uses a soft rubber flange (“cervical tab”) around the insertion catheter which is larger than the cervical opening. This prevents insertion of the catheter beyond a predetermined depth into the uterus. The apparatus is configured such that when the catheter is inserted until this cervical tab rests against the proximal cervical opening, the associated treatment balloon can deploy to treat the indicated range of uterine sizes and volumes. Before treatment, the operator confirms by examination that the uterine depth and volume fall within this predetermined range, then the operator simply inserts the balloon until the cervical tab rests against the cervix. The operator does not need to change the depth of insertion or manner of use for different patients. As a result, there is minimal risk of perforating the uterus and treatment methodology is greatly simplified for the user.
A further object of the invention is to provide a means of preventing any treatment to the cervical canal. This is achieved by a thermal insulating sheath, which surrounds the liquid delivery catheter. When the treatment balloon and liquid delivery catheter are inserted such that the cervical tab rests against the cervix, the insulating sheath located distal to the cervical tab is precisely positioned within the cervical canal. This sheath has thermal insulating capabilities, which limit the heat transfer between the liquid delivery catheter and the patient's cervix and prevents unwanted treatment of this area.